Advanced test methods of material property characterization:high strain-rate testing and experimental simulation of multiaxial stress states

Optimum utilization of the loading capability of engineering materials is an important and active contribution to protect nature's limited resources,and it is the key for economic design methods.In order to make use of the materials' resources,those must be known very well;but conventional test methods will offer only limited informational value.The range of questions raised is as wide as the application of engineering materials,and partially they are very specific.The development of huge computer powers enables numeric modelling to simulate structural behaviour in rather complex loading environments-so the real material behaviour is known under the given loading conditions.Here the art of material testing design starts.To study the material behaviour under very distinct and specific loading conditions makes it necessary to simulate different temperature ranges,loading speeds, environments etc.and mostly there doesn't exist any commonly agreed test standard.In this contribution two popular,non-standard test procedures and test systems will be discussed on the base of their application background,special design features as well as test results and typically gained information:The demand for highspeed tests up to 1000 s^(-1) of strain rate is very specific and originates primarily in the automotive industry and the answers enable CAE analysis of crashworthiness of vehicle structures under crash conditions.The information on the material behaviour under multiaxial loading conditions is a more general one.Multiaxial stress states can be reduced to an equivalent stress,which allows the evaluation of the material's constraint and criticality of stress state.Both discussed examples shall show that the open dialogue between the user and the producer of testing machines allows custom-tailored test solutions.

Optimal Design and Dynamic Simulation of Mountain Bike with Rear Suspension

This paper investigates the dynamic design methodology of mountain bikes with rear suspension. Firstly, a multi-rigid body dynamic model of rider and mountain bike coupled system is constructed. The rider model includes 19 skeletons, 18 joints and 118 main muscles. Secondly, to validate the feasibility of the model, an experiment test is designed to reflect the real cycling status. Finally, aiming at enhancing the performance of the rider vibration comfort, the scale parameters of rear suspension are optimized with computer simulation and uniform design. The mathematical model in the vibration performance and the design variables is constructed with regression analysis. The result shows that when the length of side link is 90 mm, the length of connected rod is 336.115 1 mm and the included angle between absorber and side link is 60°, the mountain bike has better vibration comfort. This study and relevant conclusions are of practical importance to the design of the mountain bike＇s rear suspension system.

Investigation into precision engineering design and development of the next-generation brake discs using Al/SiC metal matrix composites

Substantially lightweight brake discs with high wear resistance are highly desirable in the automotive industry.This paper presents an investigation of the precision-engineering design and development of automotive brake discs using nonhomogeneous Al/SiC metal-matrixcomposite materials.The design and development are based on modeling and analysis following stringent precision-engineering principles,i.e.,brake-disc systems that operate repeatably and stably over time as enabled by precision-engineering design.The design and development are further supported by tribological experimental testing and finite-element simulations.The results show the industrial feasibility of the innovative design approach and the application merits of using advanced metal-matrix-composite materials for next-generation automotive and electric vehicles.

Zemax-Based Optimum Structural Design of Probe of an Optical-Fiber Sensor

Bubble plumes are important during the process of air-sea exchange,and optical-fiber phase detection is a suitable way to observe bubble plumes entrained by breaking waves.This paper designs a new optical-fiber probe(OFP)made of sapphire to overcome the limitations of existing materials(e.g.,high brittleness,poor corrosion resistance,and narrow bandwidth)and thereby enhance the detection performance of the OFP by improving its structure.Based on total internal reflection and light refraction,a simulation model of the probe is established in the Zemax optical design software to optimize the probe tip and matching mode of the two probe tips.The results show that the optimum OFP tip is a conical sapphire one with a cone angle of 35°.Tests are then conducted on a bespoke OFP sensor,the results of which are consistent with those predicted theoretically.The simulation results lay the foundation for the integrated design of OFP sensors and the optimization of their internal optics.The findings could also be applied to OFPs with multiple tips.

Multi-parameter optimization design, numerical simulation and performance test of mixed-flow pump impeller

On the basis of the three-dimensional design platform of the mixed-flow pump impellers, an optimization design system was developed in this paper by improving the genetic algorithm with application of both strategies of keeping the optimal individu- al and employing the niche. This system took the highest efficiency of the impeller as the optimization objective and employed P, a0, A0h and A0t, which could directly affect the shape and the position of the blade, as optimization parameters. In addition, loss model was used to obtain fast and accurate prediction of the impeller efficiency. The optimization results illustrated that this system had advantages such as high accuracy and fine convergence, thus to effectively improve the design of the mixed-flow pump impellers. Numerical simulation was applied to determine the internal flow fields of the impeller obtained by optimization design, and to analyze both the relative velocity and the pressure distributions. The test results demonstrated that the mixed flow pump had the highest efficiency of 87.2%, the wide and flat high efficiency operation zone, the relatively wide range of blade angle adjustment, fine cavitation performance and satisfied stability.

Reverse design and tests of vegetable plug seedling pick-up mechanism of planetary gear train with non-circular gears

In the previous research,the seedling pick-up mechanism of the planetary gear train with incomplete eccentric circular gear and non-circular gears for vegetable plug seedlings still has two shortcomings.One is that not enough seedling pick-up depth leads to a low success ratio of seedling pick-up at high rotation speeds,the other is that the smaller seedling pushing angle results in poor seedling pushing effect.Therefore,the reverse design of the seedling pick-up mechanism based on its motion trajectory was carried out.The local trajectory of seedling pick-up and seedling pushing sections was adjusted to obtain the theoretical motion trajectory of the seedling pick-up mechanism.The cubic non-uniform B-spline curve was used to fit the adjusted trajectory.A novel seedling pick-up mechanism of the planetary gear train with non-circular gears was proposed,including three combined non-circular gears,four non-circular gears,one planetary carrier,and two seedling pick-up arms.The reverse design model of the mechanism was established.The analysis and design software of the mechanism was developed to obtain the mechanism parameters meeting design requirements.The virtual prototype of the mechanism was established and its physical prototype was manufactured.Through the virtual motion simulation and high-speed photographic kinematics bench tests of the mechanism,the kinematic model and results of reverse design of the mechanism were verified,with the kinematic performances of the mechanism prototype studied.The seedling pick-up tests of the mechanism were conducted in the laboratory.The success ratios of seedling pick-up were 94.2%,95.6% and 90.2% while the seedling pick-up efficiencies of the mechanism were 60,80 and 100 plants per minute per row,respectively.Besides,the seedling pushing effect was improved mush because of the greater seedling pushing angle.The seedling pick-up mechanism through revise design is of high value to be applied in the practical vegetable plug seedling transplanters.

Investigation on optimization design of equivalent water depth truncated mooring system

The oil industry is now increasingly concentrating their efforts and activities in connection with de- veloping fields in deeper waters, ranging typically from 500 m to 3000 m worldwide. However, the modeling of a full-depth system has become difficult presently; no tank facility is sufficiently large to perform the testing of a complete FPS with compliant mooring in 1000 m to 3000 m depth, within rea- sonable limits of model scale. Until recently, the most feasible procedure to meet this challenge seems to be the so-called "hybrid model testing technique". To implement this technique, the first and im- portant step is to design the equivalent water depth truncated mooring system. In this work, the opti- mization design of the equivalent water depth truncated mooring system in hybrid model testing for deep sea platforms is investigated. During the research, the similarity of static characteristics between the truncated and full depth system is mainly considered. The optimization mathematical model for the equivalent water depth truncated system design is set up by using the similarity in numerical value of the static characteristics between the truncated system and the full depth one as the objective function. The dynamic characteristic difference between the truncated and full depth mooring system can be minished by selecting proper design rule. To calculate the static characteristics of the mooring system, the fourth order Runge-Kutta method is used to solve the static equilibrium equation of the single mooring line. After the static characteristic of the single mooring line is calculated, the static charac- teristic of the whole mooring system is calculated with Lagrange numerical interpolation method. The mooring line material database is established and the standard material name and the diameter of the mooring line are selected as the primary key. The improved simulated annealing algorithm for continual & discrete variables and the improved complex algorithm for discrete variables are employed to per- form the optimization calculation. The C++ programming language is used to develop the computer program according to the object-oriented programming idea. To perform the optimization calculation with the two algorithms mentioned above respectively and the better result is selected as the final one. To examine the developed program, an example of equivalent water depth truncated mooring system optimum design calculation on a 100,000-t, turret mooring FPSO in water depth of 320 m are performed to obtain the conformation parameters of the truncated mooring system, in which the truncated water depth is 160 m. The model test under some typical environment conditions are performed for both the truncated and the full depth system with model scale factor λ=80. After comparing the corresponding results from the test of the truncated system with those from the full depth system test, it’s found that the truncated mooring system design in this work is successful.

基于FLAC3D模拟的14103辅运顺槽支护参数设计

针对拟施工的麻家梁矿14103辅运顺槽掘进工作面掘进期间受邻近工作面采动影响大、围岩稳定性差等问题,基于FLAC3D数值模拟计算手段,在不考虑原岩应力的影响下,对不同条件下锚杆的预应力与间距进行了模拟分析,通过对比预应力场扩散的范围与支护效果,确定了锚杆较为合适的预应力为80kN,间距为0.95m,在该支护方案下,巷道围岩整体稳定性良好,数值模拟结果显示,随着邻近工作面的回采,14103辅运顺槽顶板最大下沉量为45mm,巷道变形程度能够满足工作面正常生产需求。

管座角焊缝PAUT检测试块设计

油气工艺管线的管座多采用小径厚壁的特殊形貌结构,进行PAUT检测时需要严格进行灵敏度校准和工艺验证,才能保证检测结果准确性和可靠性。目前没有标准明确地规定管座角焊缝PAUT校准和工艺验证所需的对比试块和模拟试块,因此针对油气工艺管线管座角焊缝的特殊性,通过对管座尺寸、检测工艺、信号干扰、缺陷类型、缺陷尺寸等因素进行理论和实用性分析,首次提出并设计了一套管座角焊缝专用对比试块和模拟试块设计规则。设计出的专用对比试块成功消除了体积信号干扰,满足了小管径、大角度、高深度的校准需求;模拟试块能够完成不同缺陷类型的工艺的验证。试块应用效果良好,填补了管座PAUT试块设计的空白,为PAUT检测适用性和管座角焊缝无损检测自动化发展提供了支持。

太阳电池阵基板在热真空试验中微弱热变形测量试验研究

该文主要内容研究的是在真空冷黑环境下,通过空间外热流模拟的方式结合数字化摄影测量的手段对太阳电池阵基板的微弱变形量进行测试试验研究。试验方案中采用非接触式红外灯阵模拟空间外热流的方式,同时使用空间环境模拟设备建立试验所需的真空冷黑环境,对太阳电池阵基板进行热流的施加,试验过程中采用数字化摄影测量对不同外热流作用下造成的太阳电池阵基板的微弱热变形进行测量。试验结果表明,在红外灯阵辐射热流的作用下,太阳电池阵基板2 m×1.44 m范围内的热变形测量精度优于0.05 mm,该指标可以满足测量精度要求,光学摄影测量方法可作为测量太阳电池阵基板在热真空试验过程中微弱变形的测量方法,并且试验验证该方法有效,解决热真空试验过程中太阳电池阵基板热变形测量的问题,为后续电池阵表面设计盖片及盖片之间银连片设计提供试验数据支撑。

大巷煤柱工作面过空巷矿压规律及控制技术

【目的】由于矿井工作面布置方式的调整,煤柱工作面经常会面临通过废弃巷道时覆岩顶板难以控制的情况。【方法】为解决这一问题,以河南赵固二矿二盘区外侧煤柱工作面过空巷为工程背景,采用理论分析、数值模拟和现场试验等方法,研究工作面与空巷覆岩破断组合结构,模拟不同支护强度下顶板应力-位移全周期演化规律,分析工作面矿压显现特征,提出相应的控制技术。【结果和结论】结果表明,基本顶不同破断形式对矿压显现特征影响显著,关键块断裂位置可分为煤柱上方、空巷上方和实体煤上方3种类型。通过建立工作面过空巷力学模型,研究基本顶超前破断力学机理,基本顶受到空巷-煤柱-工作面支护系统支撑作用,形成“砌体梁”稳定承载结构,判定基本顶滑落失稳时空巷支护强度的临界值为4.6MPa。数值模拟显示,工作面超前支承压力与空巷应力集中产生的叠加效应对煤柱影响显著,当工作面推进至距空巷5m时,煤柱失稳破坏,基本顶易发生超前破断。在工作面过空巷过程中,煤柱超前支承压力分布特征由“双峰型”转变为“孤峰型”。不同支护强度下的顶板应力分布特征存在明显差异,确定空巷支护强度为4.5MPa能够防止基本顶超前破断。最后,在研究区二盘区外侧煤柱工作面采用“锚网索”支护方式对空巷顶板进行补强支护,过空巷期间液压支架工作阻力在研究区域处于安全范围内,未发生顶板垮落和压架等事故,解决了二盘区外侧煤柱工作面过空巷技术难题,可为类似工作面提供参考依据。

土动力学与岩土地震工程

社会发展需求的增长、工程建造能力的提升以及气候变化等环境因素的改变带来的新震害现象、技术手段和工程需求,为土动力学及岩土地震工程研究提出了新挑战并创造了新机遇。文章重点针对近年来土动力学与岩土地震工程领域的一些新现象、新手段和新挑战进行综述,聚焦于土的动力特性、砂土地震液化、土的动力测试和岩土地震工程试验、岩土地震工程数值模拟以及岩土工程抗震等方面,分析当前理论研究和工程实践所面临的新问题和新挑战,梳理近年来所取得的一些最新进展,并对今后的研究方向进行探讨。

多因素影响下巷道围岩稳定性分析及优化设计研究

针对深部煤层巷道矿压显现剧烈且巷道变形难以控制的问题,基于Kastner公式对巷道高宽比、侧压系数、埋深、断面形状、围岩强度5种影响巷道围岩稳定性的因素展开正交数值模拟实验,通过方差和直观分析图法研究了各因素对巷道变形破坏的敏感性。采用平面弹性复变函数理论分析了不同侧压系数与巷道高宽比下椭圆和矩形巷道围岩的应力分布规律,对椭圆形和矩形巷道宽高比和形状进行了优化设计。研究结果表明:围岩强度与侧压系数是影响巷道围岩稳定性的主要因素,埋深、断面形状、巷道高宽比为次要因素;椭圆形巷道在等轴应力比下围岩应力差值最小;矩形巷道宽度为5 m、高宽比为0.6左右时,应力集中程度较小;针对矩形巷道应力快速增高区,在考虑承压特性和断面利用率的基础上设计了圆角矩形优化巷道,确立了圆角半径的计算公式,通过数值模拟验证了其良好的性能。

深部煤岩冲击地压多功能物理模拟试验系统研制与应用

为了深入研究深部地层煤岩体冲击地压及岩爆灾害致灾规律,自主研制了深部煤岩冲击地压多功能物理模拟试验系统。该系统主要由真三轴荷载加载系统、剪切加载扰动系统、油源与增压器系统、试件制作与输运系统、试验控制与数据采集系统构成。基于该系统开展了300 mm×300 mm×600 mm的粉砂岩及相似材料试验研究。试验结果表明:测试及功能试验证明系统具有良好的准确性和稳定性,能够较高质量的完成真三轴荷载试验,位移及力传感器测试精度良好,同时该系统能完成临空面冲击破坏试验和剪切扰动试验,破坏效果直观显著;巷道破坏现象与红外热成像云图呈现了较为一致的规律,破碎区域能量释放,温度云图颜色加深。整个应力加载阶段整体平均红外辐射温度逐渐增加,进入扰动加载期温度急剧增加;在临近全面破坏时巷道内部裂纹贯通,大量围岩从巷道壁面抛出,声发射计数和能量突增,并且保持在较高水平,声发射累计能量呈指数型增长。电磁辐射能量主要发生在扰动加载阶段的破裂期与全面破坏期,在全面破坏期呈现了明显的能量幅值急剧增加的现象,与声发射能量增幅较为相似,证明了冲击失稳破坏能量的剧烈释放。

巷道围岩应力应变仿真系统设计与教学探索

为了获得采动条件下巷道围岩应力应变演化特征,通过复变函数换算结合工程实践经验,运用科学计算软件编程对巷道围岩受力模型进行求解,获得巷道围岩主应力和主应力集中系数分布规律。采用MATLAB对巷道受力模型进行模拟演算,获得工程开采参数与巷道围岩应力应变的关系规律,由此设计了一种采动影响下巷道围岩应力应变模拟仿真系统。该系统可对多种巷道断面进行计算和模拟,进而呈现出多种信息仿真演示,解决了以往软件适用巷道类型单一、应力求解不具体且结果呈现单一化缺点,可为回采巷道支护设计提供相应的理论依据,有利于矿山工程技术人员及实验室技术人员开展模拟仿真教学。

重载铁路双柱式桥墩加固技术优化研究

为探索基于性能提升的桥墩加固优化设计方法,以重载铁路中数量较多的分离式双柱式桥墩为对象,基于数值模拟分析和桥墩加固运营性能试验,开展3种常用方法加固条件下的桥墩静力性能对比分析和动力性能对比试验研究,并进行加固技术优化研究.结果表明,设计荷载作用下,墩身外包加固抑制墩顶水平位移效果较好,而"增大基础和增补桩基"组合加固则能有效减少基底截面应力;运营列车作用下,3种方法加固条件的墩顶横向振幅较加固前均有不同程度降低,但也有部分桥墩受施工等因素影响出现振幅增大的情况.采用优化提出的"增大基础+增补桩基+墩身外包"三重加固法,墩顶横向振幅降低幅度超过50%,能够很好地满足重载铁路双柱式桥墩强化改造需求.

链式海底地震仪节点结构设计与试验

海底地震仪是一种重要的海洋地震观测设备。针对中国近岸浅海洋流噪声大和人类活动频繁的特点,提出链式地震观测方式并对链式海底地震仪节点进行机械结构设计。首先根据内部构件尺寸与布局对地震仪节点整体结构进行设计;然后通过理论计算与有限元仿真方式确定地震仪节点仓体的壳体厚度、端盖厚度和密封尺寸;最后通过压力试验验证所设计的地震仪节点结构的耐压和水密性能符合要求,通过地震观测对比试验验证其接收天然地震的能力。此链式海底地震仪未来将应用于浙江近海的实际地震观测,提供实时连续的地震观测数据。

草莓大棚开沟起垄刀具数值模拟与工作参数响应面优化

草莓种植要求采用高垄栽培,为了提高开沟质量,现有开沟刀具一般是将旋耕刀具的刀身部分进行简单加宽处理。由于这种改进缺乏设计依据,当前的草莓大棚开沟刀具普遍存在作业质量不高和能耗较大的问题。为了进一步提高草莓大棚开沟刀具的性能,采用LS-DYNA软件建立了开沟刀具土壤旋抛数值仿真模型,并搭建田间实时试验装置,对仿真模型进行了分析验证。在此基础上,采用Box-Behnken响应面分析方法,以刀辊扭矩和残留粒子比例为响应值,建立了刀辊前进速度,刀轴转速和开沟起垄深度的二次回归模型,并对其进行优化。优化结果表明:前进速度0.38 m·s^(-1)、刀轴转速300 r·min^(-1)、开沟起垄深度300 mm,以此参数进行田间试验得到的扭矩为27.9 Nm,模型优化预测结果与田间试验相比相对误差小于5%,验证了优化模型和结果的可靠性。提出的新型的开沟刀具参数化设计方法可为大棚草莓开沟机具的设计优化提供参考。

轨道交通地下单渡线配线区间烟控实测及模拟研究

为了明确单渡线配线区间不同排烟设计方案的烟气控制效果,选取某地铁线路的单渡线配线区间,通过现场实测和烟流数值模拟分析,得到影响隧道区间整体排烟能力和气流组织分配的因素。结果表明:单渡线形式下,隧道通风系统的排烟能力主要取决于TVF风机,在无射流风机且仅靠TVF风机的情况下,采用2送2排模式,能满足火灾区段断面风速的要求,且均未发生烟流通过渡线串线的现象;TVF开启台数对起火区间的风速提升显著,但采用4送4排模式会导致烟气过站。

海水激活电池电解液流动特性分析

针对海水激活电池极板间电解液分布不均及电解液流量适配问题,提出一种新型仿生鹿角型流道结构,利用正交设计及计算流体力学(computational fluid dynamics,CFD)方法,研究多因素交互作用下海水激活电池内部电解液的流动特性,并对电解液流道优化进行研究。结果表明:对电解液流动特性影响最大的是流道数目,其次是电解液流量和流道偏转角;流道数目、电解液流量和流道偏转角的最佳匹配值分别是12个、200 ml/min和20°;对流道结构进行优化后,明显提升了极板间电解液的分布均匀性,调峰效率达到36.2%。研究结果能够为海水激活电池流道结构优化设计提供参考价值。